Larry Dighera wrote:
On Tue, 15 Apr 2008 22:35:03 GMT, wrote in
:

Larry Dighera wrote:
On Tue, 15 Apr 2008 17:45:04 GMT, wrote in
:

Another limitation is that for something the size of a C-172, your
battery has to deliver around 120 kW to get off the ground and
climb to altitude.


I don't see that fact as being too limiting. Why do you feel that's
an issue?

Big wires your battery has to deliver that much power without going
up in flames, yet be light enough to carry on an airplane.


If the electric motor, controller, battery, and fuel-cell are sited in
close proximity to each other (al la Sonex), the connecting bus can be
kept reasonably short. As in IC engine powered aircraft, there is the
necessity to dump waste heat to the atmosphere. The electric motor,
controller, and Li-ion battery are quite efficient, but they do
generate considerable heat at the power level you chose as an example
(C-172; ~166 HP). Here's John Monnett describing the system:

Why in the world would you have a battery and a fuel cell, ignoring
for the moment that neither is practical for aircraft use?

Any waste heat just makes the problem worse. Neither batteries nor
fuel cells have the energy density required with 100% efficiency,
much less with energy ****ed away as heat.

The big wires have to be IN the battery. You think nano wires are
going to carry 120 kW?

http://www.youtube.com/watch?v=P8Pb_psj1A8
Sonex Electric Powered Flight, EAA AirVenture Oshkosh 2007
John Monnett

Of course there is always the potential for fire when dealing with
volatile or reactive fuels as we've been discussing. Engineers have
been reasonably successful in designing systems that minimize the
probability of that hazard. That would, of course, part of the
development goal.

As a "back of the envelope" hack at the practicability of an hydrogen
(/oxygen) fuel-cell powered electric aircraft employing present day
technology, I'd say it looks worth an effort if for no other reason
than to be ready to exploit future technical discoveries as they are
made.

A lab toy and press release fodder, nothing else for the forseeable
future.

snip

You've got to start somewhere, right?

Why?


At this time in the history of civilization, with the planet's finite
petroleum reserves being pumped at ever higher volume, and the onset
of climate change, it would seem prudent to have the power to produce
a non-polluting, renewable-energy powered aircraft (in the event
anti-gravity technology doesn't become practicable BG) before the
use of our present fuel becomes impractical.

Why?

It makes more sense to put the effort into producing cheap electricity
on the ground, which has a much better chance of sucess, then synthesize
engine fuel with it.


Diesel airplanes sound like a lot better idea than electric or hydrogen
airplanes to me, plus the technology to do it exists now.


It not only exists, you can currently purchase diesel converted
Cessnas. I'm not considering becoming involved in an electric
project, but it does look like electric may actually be achievable.

Not a chance. The electric airplane, not the diesel.

Diesel airplanes need some refinement to be generally usefull.

Electric and hydrogen airplanes need new and major basic science
breakthroughs which may not ever occur and right now are nothing
more than a pipe dream.

I believe Boeing's recent effort has demonstrated that electric fuel
cell aircraft motive power is achievable with current technology.
Hopefully Boeing's demonstration will provide some impetus toward
improvement and refinement.

Well, sure, if you goal is to spend a huge pile of money to get a
motor glider up 3000 feet.

The Boeing demo was PR for military products, pure and simple.


--
Jim Pennino

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